Sunday is the 14th Annual No Pants Subway Ride

If you're heading out on Sunday and don't know what to wear, stop thinking. January 11th is the 14th annual No Pants Subway Ride, the one day each year when the metro system is clothing-optional.

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Organized by Improv Everywhere, the first No Pants Subway Ride was in 2002 and featured seven pantsless participants. According to the group, tens of thousands of people left their pants at home last year.

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What are the rules? According to Improv Everywhere, "Random passengers board a subway car at separate stops in the middle of winter without pants. The participants do not behave as if they know each other, and they all wear winter coats, hats, scarves, and gloves. The only unusual thing is their lack of pants."

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People in cities from Atlanta to Mexico City to Warsaw are planning to participate. See the complete list.

ALY SONG/Reuters/Landov/China

In previous years it's even spread to China, though it doesn't look like anyone told this guy's fellow passengers.